The present invention relates to a pneumatic power wrench of the type comprising a housing, a rotation motor drivingly connected to an output spindle, a pressure air supply passage in the housing connecting said motor to a pressure air source, a throttle valve and an adjustable pressure regulator both disposed in said air supply passage to control the air flow through the latter, and an exhaust passage connecting said motor to the atmosphere and including a flow restricting silencing means located at the downstream end of said exhaust passage.
The object of the invention is to accomplish an improved pneumatic power wrench of the above type in which the pressure regulator is arranged to provide a constant air supply pressure not only in response to a the setting of a spring biased relief valve but also in response to the pressure level in the exhaust passage upstream of the silencer. This means that notwithstanding the pressure drop across the silencer the pressure drop accross the motor will always be the same.
Further objects and advantages of the invention will appear from the following description and the claims.